A shocking video which appears to show a randy couple having sex on a train station platform could have all just been one big prank.

The footage, which disgusted onlookers forced to watch the pair getting down and dirty, has not been ruled out as a "prank or social experiment" according to Barcelona Metro.

In the clip, passionate pair kept their tops on but threw their trousers on the ground so they could make love on one of the benches normally reserved for commuters waiting for their transport to arrive.

The unbelievable scene took place in the early hours of Sunday morning at Barcelona’s Liceu station , which is under the famous La Rambla in the centre of the old part of the city known as the Gothic Quarter.

The randy couple have sex in full view of train passengers

But although the video looks genuine, some observers have questioned whether it was a set up and another social network experiment to see how people would react.

Barcelona Metro said all possibilities were being looked at, including a drunken episode, and they could not rule out the possibility that it was a prank.

The area is extremely popular with tourists and Brits on stag and hen weekends.

A local can be seen walking past in the footage, trying to ignore the X-rated scene unfolding just inches away from him.

The tube station in Barcelona (Photo: Wikipedia)

Another group of youngsters walking in the opposite direction stop as they approach the amorous couple and decide to wait until they have finished in-between embarrassed giggles.

A friend of the person who filmed the footage told Catalan daily El Periodico: “We are fed up with these sorts of situations and that’s why we’ve decided to register a formal protest and go public with it.”

It was unclear last night if the pair let their emotions get the better of them after too much to drink or were acting out their passions for a dare.